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2011
The behaviour of the turbulence in magnetic fusion plasmas is discussed in the framework of dimensional analysis. Three main dimensionless parameters are identified, which directly affect the adiabatic response of the plasma and hence control the electron response. They were originally introduced by Scott [B. Scott, Plasma Phys Control. Fusion, 39,…
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2011
Mechanisms of arc formation have been analyzed and the critical electric fields for the multipactor effect calculated, compared to the experimental values and found to be within the normal operational space of the LH system on JET. It has been shown that the characteristic electron energy (20-1000)eV for the highest multipactor resonances (N=4-9) a…
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2011
Transport analysis of MAST discharges indicates that ion collisional transport is an important loss mechanism in the core of a spherical tokamak. In the strongly-varying equilibrium fields of spherical tokamaks many of the assumptions of drift kinetic and neoclassical theory (e.g. small plasma inverse aspect ratio and low ratio of toroidal Larmor r…
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2011
The structure and phase stability of binary tungsten-vanadium and tungsten-tantalum alloys are investigated over a broad range of alloy compositions using ab initio and cluster expansion methods. The alloys are characterized by the negative enthalpy of mixing across the entire composition range. Complex intermetallic compounds are predicted by ab i…
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2011
The sawtooth instability in tokamak plasmas results in a periodic reorganization of the core plasma. A typical sawtooth cycle consists of a quiescent period, during which the plasma density and temperature increase, followed by the growth of a helical magnetic perturbation, which in turn is followed by a rapid collapse of the central pressure. The …
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2011
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2011
When testing the SHAD system on JET ICRF antennas, parasitic signals in the detection band (5-20MHz) were detected. We have identified emission from grid breakdown events in the Neutral Beam injectors, and Ion Cyclotron Emission from the plasma. Spurious signals in the band 4-10 MHz are also often observed at the onset of ELM events. Such parasitic…
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2011
Magnetic Cluster Expansion model is developed for bcc Fe-Cr alloys, and applied to the investigation of magnetic properties of these alloys for a broad interval of concentrations ranging from pure Fe to pure Cr, and for a broad interval of temperatures extending well over 1000 K. Finite-temperature configurations simulated using the Magnetic Cluste…
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2011
We present particle-in-cell (PIC) simulations of minority energetic protons in deuterium plasmas, which demonstrate a collective instability responsible for emission near the lower hybrid frequency and its harmonics. The simulations capture the lower hybrid drift instability in a regime relevant to tokamak fusion plasmas, and show further that the …
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2011
Nanoscale prismatic loops are modeled via a partial stochastic differential equation that describes an overdamped continuum elastic string, with a view to describing both the internal and collective dynamics of the loop as a function of temperature. Within the framework of the Langevin equation, expressions are derived that relate the empirical par…
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